equation for downloaded file and time taken into mbps???

i am making a internet speed test function for the rest of my script.
i have successfully downloaded the 1mb file or 10mb file optional
and i have the seconds it has taken
could somebody tell me how to convert this please.
i have a feeling its something like devide filesize by time taken then multiply by 8 but that just dont look right.
also i am looking for whole numbers like 0 1 2 3 ect
chears